Support for social networks without og:description

[ForNeVeR]

(Extracted from #170)

Some socials (suck as Skype) doesn't support og:description and draws only lone image and page title when the quote is shared into them. My current idea is to render a special text-filled images to be pasted into the Skype.

So, we need to determine whether we can implement it without hurting all other social network experience (we don't wanna to replace og:image with Skype-only crap).

If that's impossible, the issue should be dropped.